1. Field of the Invention
The present invention relates to a driving attention amount determination apparatus, method, and computer program which determines the state of attention of a driver by utilize correspond an electroencephalogram and provides safe driving assistance.
2. Description of the Related Art
In recent years, in connection with accident prevention apparatuses related to automobile driving, methods of determining the state of a driver, and providing driving assistance based on the result of determination are being studied. One visual perception function of a driver that is necessary for safe driving is detection of dangerous objects. Detection of dangerous objects involves noticing, in the peripheral visual field, any dangerous motion of vehicles and pedestrians in the surroundings. A deterioration in this function may lead to cross-collision accidents and rush-out accidents.
A “peripheral visual field” generally refers to, within the entire field of vision defined by a range spanning 130 degrees in up and down directions and 180 degrees in right and left directions, the range outside a range of about 40 degrees (central visual field) that is centered around a line of sight. As is known, in the peripheral visual field, it is difficult to recognize the shape and color of an object in detail, but sensitive response occurs with respect to any object that changes in time, e.g., a moving object or flickering light. In anticipation of a rushing out of a pedestrian or a motorcycle passing on the side, etc., a driver needs to pay attention to the peripheral visual region and any door mirrors or the like existing in this region. Therefore, when the amount of attention of the driver to the peripheral visual region becomes low, a remedy such as issuing an alarm to the driver is needed.
One method of determining the state of attention of a driver employs a camera which is aimed at the driver for detecting the line of sight and motions of the face of the driver, and determines an allocation of attention of the driver. For example, Japanese Laid-Open Patent Publication No. 2004-178367 discloses a technique of determining the attention allocation of a driver by comparing a fixation point, which is detected from the line of sight and motions of the face of the driver, against an optimum fixation position that the driver should pay attention to, which is determined from the ambient situation of the driver's vehicle.
Another method determines the state of attention of a driver based on changes in the traveling velocity and the steering angle of the steering wheel and the like, which reflect the manner in which the driver's vehicle is being operated. For example, Japanese Laid-Open Patent Publication No. 2002-127780 discloses a technique which determines a driver's degree of concentration on driving by using a brake response time with respect to a sudden deceleration of a car traveling that is ahead (hereinafter referred to as a “preceding vehicle”) or the like, thus determining the level of need to output an alarm to the driver.
On the other hand, studies are under way to examine the amount of attention of a driver to driving by utilizing an event-related potential (ERP) of his or her electroencephalogram. An “event-related potential” refers to a transient potential fluctuation in the brain which occurs in temporal relationship with an external or internal event. When examining the amount of attention of a driver to driving, the so-called “P300” is utilized. “P300” refers to a positive component of an event-related potential in the electroencephalogram which appears near about 300 milliseconds based on the timing of an external visual stimulation or the like as a starting point. P300 is supposed to reflect perception of, or attention to, a stimulation.
For example, “Technique for Measuring Driver's Attention Level by Using Event-Related Potentials”, Ebe et al., Automotive Technologies, Vol. 58, No. 7, pp. 91-96, 2004 (hereinafter referred to as “Non-Patent Document 1”) discloses a study concerning the measurement of an amount of driving attention by utilizing an event-related potential. In this study, in an experiment of trying to drive a vehicle so as to follow a preceding vehicle, the driver is asked to perform a task of stepping on a brake pedal of the driver's vehicle when brake lamps of the preceding vehicle are activated. Through a comparison of event-related potentials between the two experimental conditions of a travel (high-attention condition) during which the preceding vehicle applies sudden brakes and a travel during which the preceding vehicle does not apply sudden brakes (low-attention condition), it reports that the amplitude of P300 of the event-related potential increases under the high-attention condition.
However, the conventional technique described in Japanese Laid-Open Patent Publication No. 2004-178367 is based on the assumption that attention is not being paid to anywhere that the line of sight is not directed, and therefore cannot accurately determine the amount of attention of the peripheral visual region of the driver.
This will be described by taking an actual driving scene as an example. While monitoring a vehicle that is traveling ahead in his or her central visual region, a driver is simultaneously detecting the motions of flanking vehicles and pedestrians in his or her peripheral visual field. As a result, the driver determines the direction of his or her line of sight in accordance with the vehicle situation in the front as well as the neighboring situation. Therefore, with the conventional technique, it is difficult to cope with the case where the line of sight is being directed to the front while also paying attention to the peripheral visual region, for example.
Moreover, in the technique described in Japanese Laid-Open Patent Publication No. 2002-127780, since a brake response time with respect to a sudden deceleration of a preceding vehicle or the like is used, the derived degree of concentration on driving is limited to the front of the driver's vehicle, i.e., the central visual region of the driver. In an actual driving scene, it is very rarely the case that a response to an event occurring in the peripheral visual region of a driver is straightforwardly manifested in behavior such as braking. Therefore, with the conventional technique utilizing the manner in which the driver's vehicle is operated, the amount of attention of the driver to the peripheral visual region cannot be determined with a good accuracy.
Furthermore, in a conventional study which is described in Non-Patent Document 1, an event-related potential (ERP) with respect to activation of the brake lamps of a preceding vehicle is similarly used. Therefore, the amount of driving attention being measured is limited to that pertaining to the central visual region of the driver, and it is impossible to measure the amount of attention to the peripheral visual region.